P.S. My guess is that a lot of the 250 million(!) darkNXT is founder or large early adopter NXT put into "savings" accts, without realizing (or caring) about the "weak" 64 bit security
You forget about probability of huge transfer made accidentally by stakeholder to wrong account number because of NXT Client freeze, like many other users who had such issue before but with less amounts.
We would have heard about it by now if someone did lose millions of $ due to the client freeze. Besides, what mechanism can a freeze make a right account number become a wrong one ? Unfortunately, this has not been reliably replicated, so all we have are some anecdotal evidences.